1. Field of the Invention
The present invention generally relates to housings for electronic elements and/or devices, and more particularly to low profile extrusions for housing electronic elements and/or devices that emit light.
2. Background
In recent years, there have been dramatic improvements in the number and types of housings for light emitting devices. The frequency with which housings for devices and/or chips mounted onto circuit boards has similarly grown. Improvements in the housings for such devices have helped advance the development of final products incorporating mounted devices and can significantly reduce the cost and complexity of the product.
Commonly, light emitting diodes (LEDs) mounted on circuit boards are the devices used within these improved housings. LEDs are solid state devices that convert electric energy to light, and generally comprise one or more active layers of semiconductor material sandwiched between oppositely doped layers. When a bias is applied across the doped layers, holes and electrons are injected into the active layer where they recombine to generate light. Light is emitted from the active layer and from all surfaces of the LED.
Developments in LED technology have resulted in devices that are brighter, more efficient and more reliable. LEDs are now being used in many applications that were previously the realm of incandescent fluorescent or neon bulbs; some of these include displays, shelf lighting, refrigeration lighting, petroleum canopy lighting, exterior lighting, cove lighting and any other application where lighting is desirable or may be required. As a result, circuit board mounted LEDs and/or other similar devices can be used in applications in which they are subjected to environmental conditions that can degrade the device and adversely affect its functions and properties.
U.S. Pat. No. 4,439,818 to Scheib discloses a lighting strip that utilizes LEDs as the light source. The strip is flexible in three dimensions and is useful in forming characters and is capable of providing uniform illumination regardless of the characters selected for display. The strip comprises a flexible multi-layered pressure sensitive adhesive tape, having a plurality of triangle cutout sections on each side of the tape, with LEDs connected in a series with a resister. One disadvantage is that this arrangement is not durable enough to withstand the conditions for outdoor use. The flexible tape and its adhesive can easily deteriorate when continually exposed to the elements. Furthermore, this strip cannot be cut to different lengths for different, custom applications.
U.S. Pat. No. 5,559,681 to Duarte discloses a flexible, self adhesive, light emissive material that can be cut into at least two pieces. The light emissive material includes a plurality of light electrically coupled light emissive devices such as light emitting diodes. The material also includes electric conductors for conducting electric power from the source of electric power to each of the light emissive devices. While this lighting arrangement is cuttable to different lengths, it is not durable enough to withstand the conditions for outdoor use. The flexible tape and its adhesive can easily deteriorate.
LEDs have been used in perimeter lighting applications. PCT International Application Number PCT/AU98/00602 discloses perimeter light that uses LEDs as its light source and includes a light tube structure in which multiple LEDs are arranged within an elongated translucent tube that diffuses or disperses the light from the LEDs. The perimeter light is used to highlight or decorate one or more features of a structure, such as a roof edge, window, door or corner between a wall or roof section. This light apparatus, however, cannot be cut to match the length of a building's structural features. Instead, the perimeter lighting must be custom ordered or it is mounted without fully covering the structural feature. In addition, the light's tube significantly attenuates the light emitted by its LEDs, significantly reducing the light's brightness. Further, the light does not include a mechanism for compensating for the expansion and contraction between adjacent lights.
U.S. Pat. No. 5,678,335, to Gomi et al. discloses a display device having a plurality of light sources arranged along a display pattern for display by emitting light from the light sources. Each of the light sources has a light emitting diode (LED) in an open and elongated unit case. The case has a lens that disperses the light from the LEDs, at least in a lengthwise direction. The display pattern comprises a series of open grooves with the light sources attached to the grooves so that the light sources can be illuminated to illuminate the display pattern.
U.S. Pat. No. 6,042,248, to Hannah et al., discloses a LED assembly for illuminating signs having an enclosure covered by a translucent panel. Each sign includes a plurality track molding at the base of its enclosure, with the molding running along the longitudinal axis of the enclosure. Linear arrays of LEDs that are mounted on the printed circuit boards (PCBs), are mounted in the track moldings. Each track molding can hold two PCBs in parallel with each of the PCBs arranged on a longitudinal edge with the LEDs directed outward.
Different structures or housing can be used for holding electronic elements and/or devices that emit light, with some of these structures providing environmental protection of the housed components. Light from the light emitting devices can pass through surfaces of the housing, and certain materials actually reduce the effectiveness of the light emitting device by absorbing reflecting/refracting the light. Additionally, properties of the housings such as seams or lines from the manufacturing process may unfavorably affect the manner in which emitted light is cast onto a surface being illuminated.
Caps can be included over different opening for the housing to completely enclose the internal devices so as to further protect against the environment without interfering with the lighting applications of the device. However, housings may differ slightly from one another as a result of the manufacturing process or they may fluctuate in size due to heat produced from the electronic elements, making caps unable to properly conform to the housing to provide an adequate seal. Additionally, wires into the housing may be required to allow the device to function. However, providing a hole in the housing or cap(s) for the wire to pass-through can reduce the environmental protection afforded by the housing.